Time-multiplexing of multiple listening schedules and physical layer modes in a mesh network

ABSTRACT

Various embodiments disclose a method that includes: attempting to detect, with a first transceiver associated with a first node, a network discovery signal, wherein the attempting is performed according to (a) a first listening schedule associated with a first physical layer mode and (b) a second listening schedule associated with a second physical layer mode; detecting, with the first transceiver, the network discovery signal during a slot associated with the first listening schedule; and in response to detecting the network discovery signal, establishing, with the first node, a connection between the first node and the second node using the first physical layer mode.

BACKGROUND Field of the Various Embodiments

The various embodiments relate generally to wireless networkcommunications, and more specifically, to time-multiplexing of multiplelistening schedules and physical layer modes in a mesh network.

Description of the Related Art

A mesh network typically includes multiple electronic devices (referredto herein as “nodes”) that are organized in a mesh topology and connectto one another either directly or indirectly in a dynamic,non-hierarchical fashion. In a mesh network, the nodes cooperate withone another to route data to and from the different nodes within thenetwork as well as to and from devices outside the network. Meshnetworks are becoming increasingly common in a wide variety ofapplications, including, and without limitation, home security and homeautomation systems, home network systems, smart grid systems, and other“Internet-of-Things” systems.

During operation, the nodes of a mesh network are communicativelycoupled to each other by a wireless link, and communicate with eachother using a technique known as “channel hopping.” With channelhopping, a given node periodically transitions between differentchannels. The particular sequence of channels across which a given nodetransitions is referred to as a “channel-hopping sequence,” a “channelschedule,” or a “listening schedule.” In the channel-hopping sequence orlistening schedule, each channel in the sequence is associated with arespective time slot. As part of the normal operation of a mesh network,a given node can discover the listening schedules of neighboring nodesin the mesh network.

BRIEF DESCRIPTION OF THE DRAWINGS

So that the manner in which the above recited features of the variousembodiments can be understood in detail, a more particular descriptionof the inventive concepts, briefly summarized above, may be had byreference to various embodiments, some of which are illustrated in theappended drawings. It is to be noted, however, that the appendeddrawings illustrate only typical embodiments of the inventive conceptsand are therefore not to be considered limiting of scope in any way, andthat there are other equally effective embodiments.

FIG. 1 illustrates a network system configured to implement one or moreaspects of the various embodiments;

FIG. 2 illustrates a node device configured to transmit and receive datawithin the network system of FIG. 1 , according to various embodiments;

FIG. 3A is a diagram schematically illustrating a discovery techniqueusing a hybrid listening schedule, according to various embodiments;

FIG. 3B is a diagram schematically illustrating a default-mode listeningschedule, according to various embodiments;

FIG. 3C is a diagram schematically illustrating a long-range-modelistening schedule, according to various embodiments;

FIG. 3D is a diagram schematically illustrating a hybrid listeningschedule, according to various embodiments;

FIG. 4 is a flow diagram of method steps for a first node device toestablish a communication link with a second node device, according tovarious embodiments;

FIG. 5 is a diagram schematically illustrating a discovery operation forthe node device of FIG. 2 , according to various embodiments;

FIG. 6 is a flow diagram of method steps for a novel discovery operationthat enables a node to establish a communication link with a nodeincluded in a mesh network, according to various embodiments.

DETAILED DESCRIPTION

In the following description, numerous specific details are set forth toprovide a more thorough understanding of the various embodiments.However, it will be apparent to one of skilled in the art that theinventive concepts may be practiced without one or more of thesespecific details.

For a particular node to establish a wireless link with one or moreneighbor nodes and join a mesh network, the node must be in range of atleast one node of the mesh network. In addition, the joining node shouldbe configured to establish a link with nodes of the mesh network via asuitable physical layer protocol (or physical mode), such as aprescribed frequency and data rate, using an appropriate listeningschedule. To that end, devices that are intended to function as a nodeof a mesh network are usually configured with a default physical modefor communication within a mesh network.

Generally, the default physical mode of a node is set to optimize thetrade-off between the higher performance associated with a high datarate and the longer range and reliability associated with a low datarate. However, if the joining node is located too far from the nearestneighbor node and/or is subject to too much signal noise, a reliablelink cannot be established between the joining node and the meshnetwork. As a result, the joining node remains orphaned and cannot jointhe mesh network unless relocated closer to the mesh network, and/or arange extender or closer node is added to the mesh network that bringsthe joining node within range of the default physical mode.Consequently, the addition of a node to a mesh network using only adefault physical node can leave nodes orphaned.

To address these shortcomings, various techniques disclosed hereinenable a node device to join a mesh network. In some embodiments, a nodedevice that is included in the mesh network attempts to detect a networkdiscovery signal from the joining node device using a hybrid listeningschedule. The hybrid listening schedule time-multiplexes a firstlistening schedule associated with a first physical layer mode (such asa default physical layer mode) and a second listening scheduleassociated with a second physical layer mode (such as a long-rangephysical layer mode). In some embodiments, a node device attempts tojoin a mesh network with a single transceiver by performing a discoveryoperation that time-multiplexes transmission of a first networkdiscovery signal associated with a first physical layer mode of the nodedevice (for example the default physical layer mode) with transmissionof a second network discovery signal associated with a second physicallayer mode of the node device (for example the long-range physical layermode). In some embodiments, the node device initially attempts to jointhe mesh network with transmission of the first network discovery signalusing the default physical layer mode before attempting to join the meshnetwork with the discovery operation that time-multiplexes transmissionof the first network discovery signal with transmission of the secondnetwork discovery signal.

At least one technical advantage of the disclosed techniques relative tothe prior art is that, with the disclosed techniques, a node can join awireless network when positioned outside the effective range of adefault physical layer mode of nodes within the mesh network. A furtheradvantage is that, as conditions change over time in the mesh network,nodes can quickly and automatically select the best-performing physicallayer mode from multiple available physical layer modes, where in someinstances the best-performing physical layer mode has a lowerperformance than the default physical layer mode of the wirelessnetwork. These technical advantages provide one or more technologicalimprovements over prior art approaches.

System Overview

FIG. 1 illustrates a network system configured to implement one or moreaspects of the various embodiments. As shown, network system 100includes, without limitation, field area network (FAN) 110, wide areanetwork (WAN) backhaul 120, and control center 130. FAN 110 is coupledto control center 130 via WAN backhaul 120. Control center 130 isconfigured to coordinate the operation of FAN 110.

FAN 110 includes personal area network (PANs) A, B, and C. PANs A and Bare organized according to a mesh network topology, while PAN C isorganized according to a star network topology. Each of PANs A, B, and Cincludes at least one border router node device 112 and one or moremains-powered device (MPD) node devices 114. PANs B and C furtherinclude one or more battery-powered device (BPD) node devices 116.Network system 100 includes a plurality of node devices that areconfigured to communicate with each other according to the techniquesdescribed herein.

MPD node devices 114 draw power from an external power source, such asmains electricity or a power grid. MPD node devices 114 typicallyoperate on a continuous basis without powering down for extended periodsof time. BPD node devices 116 draw power from an internal power source,such as a battery or other local source (e.g., solar cell, etc.). BPDnode devices 116 typically operate intermittently and, in someembodiments, can power down for extended periods of time in order toconserve battery power. MPD node devices 114 and/or BPD node devices 116are configured to gather sensor data, process the sensor data, andcommunicate data processing results and/or other information to controlcenter 130. Border router node devices 112 operate as access points thatprovide MPD node devices 114 and BPD node devices 116 with access tocontrol center 130.

Any of border router node devices 112, MPD node devices 114, and/or BPDnode devices 116 are configured to communicate directly with one or moreadjacent node devices or node devices that are at a distance of one hop(also referred to as neighbors or neighbor node devices) viabi-directional communication links. In many instances, neighbor nodedevices may be physically closer than other node devices in networksystem 100, while in other instances, this is not the case, for exampledue to physical barriers that impede communication between physicallyproximate node devices. In various embodiments, a given communicationlink may be wired or wireless links, although in practice, adjacent nodedevices of a given PAN exchange data with one another by transmittingdata packets via wireless radio frequency (RF) communications. Thevarious node device types are configured to perform a technique, knownin the art as “channel hopping,” in order to periodically receive datapackets on varying channels. As known in the art, a “channel” maycorrespond to a particular range of frequencies. In one embodiment, anode device computes a current “transmit” or “receive” channel byevaluating a Jenkins hash function that is based on a total number ofchannels, the media access control (MAC) address of the node device,and/or other information associated with the node device. Alternativelyor additionally, in some embodiments, a node device determines atransmit or receive channel based on a listening schedule associatedwith an adjacent neighbor node device.

In operation, each node device within a given PAN can implement adiscovery protocol to identify one or more adjacent node devices or“neighbor node devices.” In such instances, a node device that hasidentified an adjacent, neighboring node device may establish abi-directional communication link 140 with the neighboring node device.Each neighboring node device can update a respective neighbor table toinclude information concerning the other node device, including the MACaddress of the other node device, as well as a received signal strengthindication (RSSI) of communication link 140 established with that nodedevice. In various embodiments, the neighbor table can includeinformation about one or more communication modes (referred to herein asphysical layer modes) that the neighbor node device is capable ofsupporting. Each physical layer mode can be associated with one or moredifferent operating parameters (e.g., data rates, modulation scheme,channel spacing, frequencies supported, listening schedule, etc.).

Node devices can compute the listening schedules of adjacent nodedevices in order to facilitate successful transmission of data packetsto such node devices. In embodiments where node devices implement theJenkins hash function, a node device may compute a “current receive”channel of an adjacent node device using the total number of channels,the MAC address of the adjacent node device, and/or a time slot numberassigned to a current time slot of the adjacent node device.

Any of the node devices discussed above can operate as a source nodedevice, an intermediate node device, or a destination node device forthe transmission of data packets. In some embodiments, a given sourcenode device can generate a data packet and then, (in mesh networktopologies), transmit the data packet to a destination node device viaany number of intermediate node devices. In such instances, the datapacket may indicate a destination for the packet and/or a particularsequence of intermediate node devices to traverse in order to reach thedestination node device. In some embodiments, each intermediate nodedevice can include a forwarding database indicating various networkroutes and cost metrics associated with each route.

Node devices 112, 114, 116 transmit data packets across a given PAN andacross WAN backhaul 120 to control center 130. Similarly, control center130 transmits data packets across WAN backhaul 120 and across any givenPAN to a particular node device 112, 114, 116 included therein. As ageneral matter, numerous routes can exist which traverse any of PANs A,B, and C and include any number of intermediate node devices, therebyallowing any given node device or other component within network system100 to communicate with any other node device or component includedtherein.

Control center 130 includes one or more server machines (not shown)configured to operate as sources for, and/or destinations of, datapackets that traverse within network system 100. In various embodiments,the server machines can query node devices within network system 100 toobtain various data, including raw and/or processed sensor data, powerconsumption data, node/network throughput data, status information, andso forth. The server machines can also transmit commands and/or programinstructions to any node device 112, 114, 116 within network system 100to cause those node devices to perform various operations. In oneembodiment, each server machine is a computing device configured toexecute, via a processor, a software application stored in a memory toperform various network management operations.

In various embodiments, node devices 112, 114, 116 can include computingdevice hardware configured to perform processing operations and executeprogram code. Each node device can further include variousanalog-to-digital (A/D) converters, digital-to-analog (D/A) converters,digital signal processors (DSPs), harmonic oscillators, transceivers,and/or any other components generally associated with RF-basedcommunication hardware. FIG. 2 illustrates an exemplary node device thatcan operate within the network system 100.

Node Device

FIG. 2 illustrates a node device configured to transmit and receive datawithin the network system 100 of FIG. 1 , according to variousembodiments. As shown, node device 210 is coupled to transceiver 250 andoscillator 260. Node device 210 includes, without limitation, aprocessor 220, input/output devices 230, and memory 240. Memory 240includes one or more applications (e.g., software application 242) thatcommunicate with database 244.

Processor 220 coordinates the operations of node device 210. Transceiver250 is configured to transmit and/or receive data packets and/or othermessages across network system 100 using a range of channels and powerlevels. Oscillator 260 provides one or more oscillation signals,according to which, in some embodiments, node device 210 may schedulethe transmission and reception of data packets. In some embodiments,node device 210 can be used to implement any of border router nodedevices 112, MPD node devices 114, and/or BPD node devices 116 of FIG. 1.

In various embodiments, processor 220 can include any hardwareconfigured to process data and execute software applications. Processor220 may include a real-time clock (RTC) (not shown) according to whichprocessor 220 maintains an estimate of the current time. The estimate ofthe current time can be expressed in Universal Coordinated Time (UTC),although any other standard of time measurement can also be used. I/Odevices 230 include devices configured to receive input, devicesconfigured to provide output, and devices configured to both receiveinput and provide output. Memory 240 can be implemented by anytechnically-feasible computer-readable storage medium.

Memory 240 includes one or more software applications 242 and database244, coupled together. The one or more software applications includesprogram code that, when executed by processor 220, can perform any ofthe node-oriented computing functionality described herein. The one ormore software applications 242 can also interface with transceiver 250to coordinate the transmission and/or reception of data packets and/orother messages across network system 100, where the transmission and/orreception is based on timing signals generated by oscillator 260. Invarious embodiments, memory 240 can be configured to store protocolsused in physical layer modes, equations and/or algorithms foridentifying metric values, constants, data rate information, listeningschedules, and other data used in identifying metric values, etc. Memory240 can also include a key store 246 where keys for encryption and/ordecryption of communications (e.g., messages) between node devices canbe stored.

In operation, software application(s) 242 can implement varioustechniques to optimize communications with one or more linked nodedevices, such as a neighbor node device. In various embodiments, nodedevice 210 can be configured to, using a plurality of differentcommunication modes, transmit data messages to the linked node deviceand/or receive data messages from the linked node device by selecting acommon communication mode (such as a physical layer mode) that issupported by node device 210 and the linked node device (e.g., any ofborder router node devices 112, MPD node devices 114, and/or BPD nodedevices 116 of FIG. 1 ). More generally, node device 210 can beconfigured for multi-mode communications. Node device 210 cancommunicate with a linked node or with control center 130 using any of aplurality of modes. The particular mode used for a given transmissiondepends on the particular circumstances of the transmission (e.g., thetype of data message, the intended recipients of the data message,etc.). Examples of the modes include, without limitation, unicast,broadcast, and multi-cast.

Hybrid Listening Schedule Using Multiple Physical Layer Modes

According to various embodiments, a node device that cannotcommunicatively link to any nodes of a mesh network via a defaultphysical layer mode attempts to join the network via a long-rangephysical layer mode. An example embodiment is depicted in FIG. 3A.

FIG. 3A schematically illustrates a discovery technique using a hybridlistening schedule, according to various embodiments. In the embodimentillustrated in FIG. 3A, a joining node device attempts to join the meshnetwork by performing a discovery operation that time-multiplexestransmission of a first network discovery signal 351 associated with afirst physical layer mode of the node device (for example a defaultphysical layer mode) with transmission of a second network discoverysignal 352 associated with a second physical layer mode of the nodedevice (for example a long-range physical layer mode). In addition, oneor more in-network node devices (node devices already included in themesh network) attempt to detect a network discovery signal (e.g., firstnetwork discovery signal and/or second network discovery signal 352)from other node devices (e.g., the joining node device) using a hybridlistening schedule. The hybrid listening schedule time-multiplexes afirst listening schedule that is associated with the first physicallayer mode and a second listening schedule that is associated with asecond physical layer mode.

In step 341, the joining node device transmits first network discoverysignal 351 via a first physical layer mode of the joining node device.In step 342, the joining device switches to a second physical layer modeof the joining node device and transmits second network discovery signal352 after not receiving a response to the first network discovery signal351. The joining node device then continues to alternately transmitfirst network discovery signal 351 and second network discovery signal352. In step 434, an in-network node device listens using a firstlistening schedule, for example via a first physical layer mode of thein-network node device. In step 344, the in-network node device switchesto a second physical layer mode of the in-network node device andlistens using a second listening schedule, for example via a secondphysical layer mode of the in-network node device. In step 345, thejoining node device transmits second network discovery signal 352, andin step 346, the in-network node device detects second network discoverysignal 352. In step 347, the in-network node device transmits linkinformation to the joining node device, such as listening scheduleinformation for the in-network node device. In step 348, the joiningnode device receives the link information. In step 349, the joining nodedevice adds the in-network node device to a neighbor table of thejoining node device.

Example embodiments of the first listening schedule, the secondlistening schedule, and the hybrid listening schedule are describedbelow in conjunction with FIGS. 3B-3D.

FIG. 3B is a diagram schematically illustrating a default-mode listeningschedule 310, according to various embodiments. Default-mode listeningschedule 310 is a default channel-hopping sequence associated with aparticular node device of a mesh network, such as node device 210 inFIG. 2 . Thus, default-mode listening schedule 310 indicates a sequenceof channels 311 that is followed by the transceiver of the particularnode device using a protocol associated with a default physical layermode of that particular node device. For example, default-mode listeningschedule 310 can indicate the timing at which each channel 311 in a setof channels 311 (or frequency bands) associated with the defaultphysical layer mode is employed in inter-node communications.

In the embodiment illustrated in FIG. 3B, default-mode listeningschedule 310 is configured with an N-channel hop sequence of N differentchannels 311 (e.g., channels 0 to N−1) that are sequenced within anepoch 312. Each of the N different channels 311 is associated with adifferent specific slot 313 within an epoch 312. For example, channel 0is employed for starting inter-node communications (e.g., listeningand/or transmitting) during slot 313A, channel 1 is employed forstarting inter-node communications during slot 313B, channel 2 isemployed for starting inter-node communications during slot 313C, and soon. Once a particular epoch 312 expires, the N-channel hop sequence ofchannels 0 to N−1 then repeats as shown. Thus, a neighbor node devicethat has knowledge of default-mode listening schedule 310 cancommunicate with the node associate with default-mode listening schedule310 via channels 0 to N−1.

FIG. 3C is a diagram schematically illustrating a long-range-modelistening schedule 320, according to various embodiments.Long-range-mode listening schedule 320 is a long-range channel-hoppingsequence associated with a particular node device of a mesh network,such as node device 210 in FIG. 2 . Thus, long-range-mode listeningschedule 320 indicates a sequence of channels 321 that is followed bythe transceiver of the particular node device using a protocolassociated with a long-range physical layer mode of that particular nodedevice. For example, long-range-mode listening schedule 320 can indicatethe timing at which each channel 321 in a set of channels 321 (orfrequency bands) associated with the long-range physical layer mode isemployed in inter-node communications.

In some embodiments, the long-range physical layer mode of a particularnode device differs from the default physical layer mode of theparticular node device by at least one operating parameter. In suchembodiments, when the node device employs the long-range physical layermode, the at least one operating parameter is selected in the long-rangephysical layer mode to enable longer-range communications between thenodes. For example, in some embodiments, a data rate associated with thelong-range physical layer mode for the particular node device is lowerthan a data rate associated with the default physical layer mode for theparticular node device. Thus, in such embodiments, data transfer betweentwo nodes employing the long-range physical layer mode is slower thandata transfer between two nodes employing the default physical layermode, but such data transfer can be performed reliably over a longerrange and/or under noisier conditions.

In the embodiment illustrated in FIG. 3C, long-range-mode listeningschedule 320 is configured with an M-channel hop sequence of M differentchannels 321 (e.g., channels 300 to M+299). Each of the M differentchannels 321 is associated with a different specific slot 323 oflong-range-mode listening schedule 320. For example, channel 300 isemployed for starting inter-node communications during slot 323A,channel 301 is employed for starting inter-node communications duringslot 323B, and so on.

In some embodiments, the M channels 321 of long-range-mode listeningschedule 320 are not interleaved in time with the N channels 311 ofdefault-mode listening schedule 310 on a one-to-one basis. Instead, insuch embodiments, a first portion of the M channels 321 oflong-range-mode listening schedule 320 is associated with a first singleepoch 312 of default-mode listening schedule 310, a second portion ofthe M channels 321 is associated with a second single epoch 312, a thirdportion of the M channels 321 is associated with a third single epoch312, and so on. As a result, the M channels 321 may be sequenced acrossa large number of epochs 312 of default-mode listening schedule 310. Forexample, in an instance in which M=20 and every two channels 321 oflong-range-mode listening schedule 320 are associated with a singleepoch 312 of default-mode listening schedule 310, the M channels 321 oflong-range-mode listening schedule 320 are distributed across ten epochs312. In such an instance, the duty cycle of the long-range physicallayer mode is relatively low. Therefore, the interleaving of the Mchannels 321 of long-range-mode listening schedule 320 with the Nchannels 311 of default-mode listening schedule 310 does notsignificantly affect the duty cycle of the default physical layer mode,which is the physical layer mode typically used for most communicationby a node device. Alternatively or additionally, in some embodiments,the periodicity of the M channels 321 of long-range-mode listeningschedule 320 is not linked to the duration of an epoch 312 ofdefault-mode listening schedule 310. Thus, in such embodiments, the Mchannels 321 can be interleaved in any technically feasible pattern andnot just a regular pattern. For example, in one embodiment, one channel321 is associated with a slot 323 that occurs during one epoch 312, twochannels 321 are associated with a slot 323 that occurs during the nextepoch 312, zero channels 321 are associated with a slot 323 that occursduring the next epoch, three channels 321 are associated with a slot 323that occurs during the next epoch 312, etc.

In the embodiment illustrated in FIG. 3C, for each slot 313 of the Mchannels 321 associated with long-range-mode listening schedule 320,there is an associated active period 325 and inactive period 326. In theactive period 325 for a slot 313 associated with a particular channel321, the transceiver of the node device listens on that particularchannel 321. That is, the transceiver of the node device attempts todetect signals on the channel associated with the active period. Bycontrast, in the inactive period 326 of the slot 313 for the particularchannel 321, the transceiver of the node device does not listen usingthe long-range physical layer mode. Further, in embodiments in whichlong-range-mode listening schedule 320 is incorporated into a hybridlistening schedule (described below in conjunction with FIG. 3D), thetransceiver of the node device listens on one or more channelsassociated with slots 313 that correspond in time to that inactiveperiod 326. For example, in the embodiment illustrated in FIG. 3C,during the inactive period 326 associated with channel 300, thetransceiver of the node device listens on channels 1-41 (which are eachassociated with default-mode listening schedule 310) using the defaultphysical layer mode.

In some embodiments, the set of channels 321 (or frequency bands)associated with the long-range physical layer mode includes a differentset of frequency bands than the set of channels 311 (or frequency bands)associated with the default physical layer mode. In other embodiments,one or more of channels 321 can have one or more frequency bands thatare the same as one or more channels 311. Alternatively or additionally,in some embodiments, the set of channels 321 associated with thelong-range physical layer mode includes a different set of frequencybands than the set of channels 311 associated with the default physicallayer mode. Alternatively or additionally, in some embodiments theduration of slots 323 associated with the long-range physical layer modecan be different than the duration of slots 313 associated with thedefault physical layer mode.

FIG. 3D is a diagram schematically illustrating a hybrid listeningschedule 330, according to various embodiments. Hybrid listeningschedule 330 is time-multiplexed combination of default-mode listeningschedule 310 (which is associated with the default physical layer modeof the node device) and long-range-mode listening schedule 320 (which isassociated with the long-range physical layer mode of the node device).It is noted that in some mesh networks, a node device generally includesa single transceiver, and therefore the transceiver of the node deviceeither transmits or receives network signals via the default physicallayer mode or the long-range physical layer mode, but not bothsimultaneously. Consequently, slots 313 (for the N channels 311) ofdefault-mode listening schedule 310 and slots 323 (for the M channels321) of long-range-mode listening schedule 320 are interleaved in time,so that operation of the transceiver of the node device switches betweena default physical layer mode and a long-range physical layer modewithin each epoch 312 of hybrid listening schedule 330. For example, inthe embodiment illustrated in FIG. 3D, slot 323A of long-range-modelistening schedule 320 occurs between slot 313A and slot 3138 ofdefault-mode listening schedule 310, slot 323B of long-range-modelistening schedule 320 occurs after slot 313D and the next subsequentslot (not shown) of default-mode listening schedule 310, and so on.Further, in the embodiment shown, the active period 325 of slots 323temporally overlap one or more slots 313 of default-mode listeningschedule 310. In such embodiments, the time interval associated withslots 323 is taken from one or more of the time intervals associatedwith slots 313. Thus, in such embodiments, in an epoch 312 of hybridlistening schedule 330 in which a particular slot 313 is temporallyoverlapped by a slot 323, the time interval associated with thatparticular slot 313 is reduced in duration compared to a time intervalassociated with that particular slot 313 in another epoch 312.Alternatively or additionally, in some embodiments, a particular slot313 that is temporally overlapped by a slot 323 is completely overlappedin time. In such embodiments, the overlapped slot 313 is not employed inthat particular epoch 312.

In some embodiments, a duration 327 of slots 323 is longer than aduration 317 of slots 313. In such embodiments, the longer duration 327of slots 323 facilitates the longer time generally required to receiveat least a header portion of a frame, packet, or other data unit from aneighbor node device. In such embodiments, duration 327 may be anintegral multiple of duration 317, and/or a combined duration of activeperiod 325 and inactive period 326 may be an integral multiple ofduration 317. Alternatively, in some embodiments, duration 327 of slots323 is substantially equal to duration 317 of slots 313. Generally,duration 317 is selected to be of a sufficient length that enables anode operating in default physical layer mode to recognize that amessage from another node device is being received by the currentlyactive channel of default-mode listening schedule 310. For example, thelength of duration 317 can be selected based on a duration of a preambleof a discovery message (not shown) transmitted in a default physicallayer mode. Similarly, duration 327 is selected to be of sufficientlength that enables a node operating in long-range physical layer modeto recognize that a message from another node device is being receivedby the currently active channel of long-range-mode listening schedule320. For example, the length of duration 327 can be selected based on aduration of a preamble of a discovery message (not shown) transmitted ina long-range physical layer mode.

In the embodiment described above in conjunction with FIGS. 3A-3C, asingle listening schedule for a long-range physical layer mode istime-multiplexed with a listening schedule for a default physical layermode. Thus, in such embodiments, operation of the transceiver of thenode device can switch between the default physical layer mode and thelong-range physical layer mode within each epoch 312 of default-modelistening schedule 310. In other embodiments, listening schedules formultiple long-range physical layer modes are time-multiplexed with thelistening schedule for a default physical layer mode. In suchembodiments, one or more slots for each long-range physical layer modeis interleaved with slots 313 of default-mode listening schedule 310.Thus, in such embodiments, operation of the transceiver of the nodedevice switches between the default physical layer mode and the multiplelong-range physical layer modes within each epoch 312 of default-modelistening schedule 310. Alternatively, in such embodiments, within someepochs 312, operation of the transceiver of the node device switchesbetween the default physical layer mode and one of the multiplelong-range physical modes, and within other epochs 312, operation of thenode device switches between the default physical layer mode and anotherof the multiple long-range physical modes.

FIG. 4 is a flow diagram of method steps for a first node device toestablish a communication link with a second node device, according tovarious embodiments. In some embodiments, the first node device is anode device that is currently included in a mesh network, and the secondnode device is a node device that is attempting to join the meshnetwork. For example, the second node device may be a node device thatis newly installed and/or initialized within range of one or more nodesincluded in the mesh network. Alternatively, the second node device maybe a node device that was previously included in the mesh network, buthas lost connection with the mesh network, for example due to changingnoise levels, mesh network traffic levels, and/or environmental or otherfactors. For example, in one such instance, the second node waspreviously linked to the mesh network via communications using a defaultmode physical layer mode, and certain factors caused the link to belost. According to various embodiments, the second node can reestablisha link to the mesh network via one or more long-range physical layermodes, as described below.

Although the method steps are described with respect to the systems ofFIGS. 1-3C, persons skilled in the art will understand that any systemconfigured to perform the method steps, in any order, falls within thescope of the various embodiments.

As shown, a method 400 begins at step 402, where the transceiver of thenode device 210 attempts to detect a network signal from neighbor nodedevices according to a hybrid listening schedule. The network signal canbe a network discovery signal (described below in conjunction with FIGS.5 and 6 ) or any other signal from a neighbor node device. In someembodiments, the node device employs hybrid listening schedule 330 instep 402. Thus, in such embodiments, operation of the node deviceswitches between a default physical layer mode and a long-range physicallayer mode, depending on whether a slot 313 of default-mode listeningschedule 310 or a slot 323 of long-range-mode listening schedule 320 iscurrently indicated by hybrid listening schedule 330.

In step 404, node device 210 detects a network discovery signal, such asa network discovery frame, from a neighbor node device. To be detected,the network discovery signal is transmitted during a particular slot 313or 323 of hybrid listening schedule 330 and via the channel that isassociated with that particular slot 313 or 323, referred to hereinafteras the “receiving channel.”

In step 406, node device 210 determines whether an initial portion ofthe network discovery frame has been received, such as a header portionthat includes metadata associated with the network discovery frame. Ifyes, method 400 proceeds to step 408; if no, method 400 returns to step402.

In step 408, node device 210 continues to listen on the channelassociated with the specific slot 313 or 323 during which the networkdiscovery signal is received in step 404. Thus, in some embodiments,node device 210 can halt attempts to detect network signals via hybridlistening schedule 330, and instead can continue to listen on thereceiving channel. In so doing, the transceiver of the node device 210continues to receive a remainder portion of the network discoverysignal. For example, in some embodiments, the remainder portion of thenetwork discovery signal includes synchronization information and/orlistening schedule information associated with the neighbor node device.

In step 410, node device 210 determines whether the complete networkdiscovery signal has been received. If yes, method 400 proceeds to step412; if no, method 400 returns to step 408.

In step 412, node device 210 extracts synchronization information andlistening schedule information from the network discovery signal. Basedon such information, the node device 210 is enabled to communicate withthe neighbor node device.

In step 414, node device 210 establishes communications with theneighbor node device. For example, in some embodiments, the joiningdevice exchanges complete link information with the node device, therebyenabling future unicast communication links to be initiated to or fromthe joining device. In some embodiments, in step 414 node device 210transmits synchronization and/or listening schedule information to theneighbor node device. In some embodiments, node device 210 establishesthe communications with the neighbor node device via the same physicallayer mode associated with the received network discovery signal. Forexample, when node device 210 detects the network discovery signal instep 404 during a slot 323 of hybrid listening schedule 330, which isassociated with the long-range physical layer mode of node device 210,node device 210 establishes communications with the neighbor node devicevia the long-range physical layer mode. Conversely, when node device 210detects the network discovery signal in step 404 during a slot 313 ofhybrid listening schedule 330, which is associated with the defaultphysical layer mode of node device 210, node device 210 establishescommunications with the neighbor node device via the default physicallayer mode.

In some embodiments, method 400 is performed continuously. Thus, in suchembodiments, upon completion of step 414, method 400 returns to step402. In other embodiments, method 400 is performed periodically, forexample once every 12 hours, 24 hours, and/or the like. In suchembodiments, steps 402-414 iterate for a predetermined time interval,e.g., 1 hour, before method 400 terminates. Alternatively oradditionally, in some embodiments, method 400 is performed in responseto a certain event, such as a restoration of power to node device 210,receipt of a notification from a neighbor node device or control center130, and/or the like.

Discovery Operation Using Multiple Physical Layer Modes

In some embodiments, a node device performs a novel discovery operationthat enables the node device to establish a link with a node included ina mesh network via a default physical layer mode when possible and via along-range physical layer mode when necessary. Specifically, thediscovery operation time-multiplexes transmission of a first networkdiscovery signal associated with a first physical layer mode of the nodedevice (for example a default mode) with transmission of a secondnetwork discovery signal associated with a second physical layer mode ofthe node device (for example a long-range mode). An example embodimentof network discovery signals transmitted via the novel discoveryoperation is described below in conjunction with FIGS. 5 and 6 .

FIG. 5 is a diagram schematically illustrating a network discoveryoperation 500, according to various embodiments. In network discoveryoperation 500, a node device attempting to join a mesh network, referredto hereinafter as a “joining device,” transmits network discoverysignals, such as network discovery frames. In addition, the joiningdevice transmits one or more network discovery signals using a defaultphysical layer mode and one or more long-range physical layer modes. Inthe embodiment illustrated in FIG. 5 , network discovery operation 500includes a default mode discovery period 510 and a long-range modediscovery period 520. In default mode discovery period 510, the joiningdevice transmits network discovery signals 511 via the default physicallayer mode of the joining device, and in long-range mode discoveryperiod 520, the joining device transmits network discovery signals 521via the long-range physical layer mode of the joining device. Because insome mesh networks the joining device generally includes a singletransceiver, the joining device either transmits network discoverysignals via the default physical layer or the long-range physical layermode, but not both simultaneously.

As shown, network discovery signals 511 are transmitted at random orsemi-random times during default mode discovery period 510, so that,after a sufficient number of attempts, an initial portion of networkdiscovery signal 511 coincides with a listening slot of a neighbor nodedevice. Thus, in such embodiments, each of network discovery signals 511is transmitted after a response period 515 has expired, where eachresponse period 515 has a duration that is randomly or semi-randomlydetermined. For example, the duration of each response period 515 may bedetermined as function of a default mode slot time, such as a randomintegral multiple of the default mode slot time. As a result, there issufficient delay between transmission of each network discovery signal511 to ensure the joining device can detect a responding node from anearby mesh network. In such embodiments, the default mode slot time maybe based on one or more operating parameters of the default physicallayer mode, such as data rate.

In some embodiments, each network discovery signal 511 of default modediscovery period 510 is transmitted via a different channel that isassociated with the default physical layer mode of node devices includedin the nearby mesh network. Thus, upon completion of default modediscovery period 510, a network discovery signal 511 can be transmittedusing each channel that is associated with the default physical layermode of node devices in the nearby mesh network. In other embodiments,in a single default mode discovery period 510, multiple networkdiscovery signals 511 are transmitted for each different channel that isassociated with the default physical layer mode of node devices includedin the nearby mesh network. In such embodiments, upon completion ofdefault mode discovery period 510, multiple network discovery signals511 have been transmitted using each channel that is associated with thedefault physical layer mode.

In some embodiments, a plurality of default mode discovery periods 510are performed in network discovery operation 500 before a firstiteration of a long-range mode discovery period 520 is performed. Insuch embodiments, the lower-bandwidth communication links associatedwith a long-range physical layer mode may not be attempted (with one ormore long-range mode discovery periods 520) until the likelihood ofestablishing a communication link via the default physical layer mode isdetermined to be less than a threshold value (multiple default modediscovery periods 510).

Network discovery signals 521 of long-range mode discovery period 520are substantially similar to network discovery signals 511 of defaultmode discovery period 510, except that network discovery signals 521 aretransmitted via a long-range physical layer mode of the joining device.For example, in some embodiments, network discovery signals 521 aretransmitted at random or semi-random times during long-range modediscovery period 520. In addition, each of network discovery signals 521is transmitted after a response period 525, where each response periodhas a duration that is randomly or semi-randomly determined. Forexample, the duration of each response period 525 may be determined as afunction of a long-range mode slot time that may be based on one or moreoperating parameters of the long-range physical layer mode, such as datarate. In an embodiment, the function includes a random integral multipleof the long-range mode slot time. As a result, there is sufficient delaybetween transmission of each network discovery signal 521 to ensure thejoining device can detect a responding node from a nearby mesh network.It is noted that the long-range mode slot time for the joining node canbe significantly longer than the default mode slot time for the joiningnode. Further, in some embodiments, each network discovery signal 521 oflong-range mode discovery period 520 is transmitted via a differentchannel that is associated with the long-range physical layer mode.Alternatively, in some embodiments, each different channel that isassociated with the default physical layer mode is used to transmitmultiple network discovery signals 521 in long-range mode discoveryperiod 520.

In some embodiments, transmission of each network discovery signal 521occurs over a longer time interval 526 than a time interval 516 employedfor transmission of each network discovery signal 511. In suchembodiments, this is generally due to node devices included in a meshnetwork typically listening via long-range physical layer mode with alower duty cycle than via default physical layer mode. As a result, theprobability is relatively small that the initial portion of a networkdiscovery signal 521 transmitted by a joining node on a particularchannel coincides with a slot for that particular channel of along-range-mode listening schedule of a node device included in a meshnetwork. By comparison, the probability is much greater that the initialportion of a network discovery signal 511 transmitted by the joiningnode on a particular channel coincides with a slot for that particularchannel of a default-mode listening schedule of the node device includedin a mesh network. Consequently, in such embodiments, long-range modediscovery period 520 can have a longer duration than default modediscovery period 510. In some embodiments, the longer duration oflong-range mode discovery period 520 may also be due in part to theslower data rate generally associated with the long-range physical layermode of the joining device relative to the default physical layer modeof the joining device.

In the embodiment illustrated in FIG. 5 , network discovery operation500 includes a single default mode discovery period 510 followed by asingle long-range mode discovery period 520. In other embodiments,network discovery operation 500 includes multiple default mode discoveryperiods 510 before one or more long-range mode discovery periods 520occur. Further, in the embodiment illustrated in FIG. 5 , transmissionof network discovery signals 511 is performed in default mode discoveryperiod 510 and transmission of network discovery signals 521 isperformed in long-range mode discovery period 520. In other embodiments,transmission of network discovery signals 511 and network discoverysignals 521 are interleaved, and occur throughout network discoveryoperation 500. Thus, in such embodiments, one or more network discoverysignals 521 may be transmitted in network discovery operation 500 priorto some or all of network discovery signals 511.

FIG. 6 is a flow diagram of method steps for a novel discovery operationthat enables a node to establish a communication link with a nodeincluded in a mesh network, according to various embodiments. Althoughthe method steps are described with respect to the systems of FIGS. 1-5, persons skilled in the art will understand that any system configuredto perform the method steps, in any order, falls within the scope of thevarious embodiments.

As shown, a method 600 begins at step 602, where a joining device beginsa discovery operation, such as discovery operation 500. In someembodiments, the discovery operation is performed in response to thejoining device being powered up or initialized, or whenever the joiningdevice determines that there is no communication link established with amesh network. Additionally or alternatively, in some embodiments, thediscovery operation is performed periodically, for example once per day,twice per week, etc., so that additional communication links can beestablished with newly installed node devices and/or higher-bandwidthcommunications links can be established with existing device in the meshnetwork.

In step 604, the joining device selects a physical layer mode for thetransceiver of the joining device. In some embodiments, the joiningdevice is configured with a default physical layer mode and a long-rangephysical layer mode. In other embodiments, the joining device isconfigured with a default physical layer mode and multiple long-rangephysical layer modes. In such embodiments, each long-range physicallayer mode differs from the other long-range physical layer modes by oneor more operating parameters. Thus, each long-range physical layer modeprovides a different trade-off between performance and range.

In some embodiments, in a first iteration of steps 604-616, the joiningdevice selects a higher-performing physical layer mode in step 604, suchas a default physical layer mode to start, for the transceiver of thejoining device. In such embodiments, in subsequent iterations of steps604-616, the joining device selects a lower-performing physical layermode in step 604, such as a long-range physical layer mode. Thus, insuch embodiments, the establishment of higher-bandwidth links isattempted prior to the establishment of lower-quality, longer rangelinks.

In some embodiments, in a first iteration of steps 604-616, the joiningdevice selects a most recently employed physical layer mode in step 604.Thus, in such embodiments, the joining device selects a physical layermode based on previous interactions with one or more nodes of a nearbymesh network. In such embodiments, a joining device that has previouslyestablished communication links via a long-range physical layer modeselects that long-range physical layer mode in a first iteration ofsteps 604-616.

In step 606, the joining device selects a channel associated with thephysical layer mode selected in step 604. In step 608, the joiningdevice determines a duration of a response period for the networkdiscovery signal to be transmitted. In step 610, the joining devicetransmits a network discovery signal, such as network discovery signal511 or 521. In step 610, the joining device transmits the networkdiscovery signal using the channel selected in step 606 and the physicallayer mode selected in step 604.

In step 612, the joining device determines whether a response isreceived during the response period to the network discovery signaltransmitted in step 610. When no response is received, method 600proceeds to step 614; when a response is received, method 600 proceedsto step 618.

In step 614, the joining device determines whether one or morecompletion criteria for the selected physical layer mode have been met.Examples of different completion criteria include: the transmission of anetwork discovery signal for each channel associated with the selectedphysical layer mode; the transmission of a specified number of networkdiscovery signals for each channel associated with the selected physicallayer mode; the transmission of a total number network discovery signalsusing the selected physical layer mode; the transmission for apredetermined time interval of network discovery signals using theselected physical layer mode; the completion of a predetermined numberof discovery periods associated with the selected physical layer mode(e.g., default mode discovery period 510 or long-range mode discoveryperiod 520); and/or the like. When such a completion criterion isdetermined not to be met, method 600 returns to step 606 and anotherchannel associated with the selected physical layer mode is selected.When such a completion criterion is determined to be met, method 600proceeds to step 616.

In step 616, the joining device determines whether there are anyremaining physical layer modes of the joining device that have not yetbeen used to send network discovery signals. When there is at least oneremaining physical layer mode, method 600 returns to step 604 andanother physical layer mode is selected. When there are no remainingphysical layer modes, method 600 proceeds to step 620 and terminates.

In step 618, the joining device establishes communications with the nodedevice that responded during the response period. For example, in someembodiments, the joining device exchanges complete link information withthe node device, thereby enabling future unicast communications links tobe initiated to or from the joining device. In step 620, the joiningdevice terminates the current discovery operation.

1. In some embodiments, a method includes: attempting to detect, with afirst transceiver associated with a first node, a network discoverysignal from a second node, wherein the attempting is performed accordingto (a) a first listening schedule associated with a first physical layermode and (b) a second listening schedule associated with a secondphysical layer mode; detecting, with the first transceiver, the networkdiscovery signal during a slot associated with the first listeningschedule; and in response to detecting the network discovery signal,establishing, with the first node, a connection between the first nodeand the second node using the first physical layer mode.

2. The method of clause 1, wherein the network discovery signalcomprises at least a header portion of a network discovery frame.

3. The method of clauses 1 or 2, wherein the network discovery signal isreceived from the second node attempting to join a network that includesthe first node.

4. The method of any of clauses 1-3, wherein the first physical layermode comprises a first data rate and the second physical layer modecomprises a second data rate that is different than the first data rate.

5. The method of any of clauses 1-4, wherein the first physical layermode comprises a first data rate and the second physical layer modecomprises a second data rate that is lower than the first data rate.

6. The method of any of clauses 1-5, wherein the second listeningschedule includes a slot that has an active period in which the networkdiscovery signal can be detected and an inactive period in which thenetwork discovery signal cannot be detected.

7. The method of any of clauses 1-6, wherein each slot included in thesecond listening schedule has a respective active period in which thenetwork discovery signal can be detected and a respective inactiveperiod in which the network discovery signal cannot be detected.

8. The method of any of clauses 1-7, wherein the inactive periodtemporally overlaps one or more slots associated with the firstlistening schedule.

9. The method of any of clauses 1-8, wherein the active period has alonger duration than the slot associated with the first listeningschedule.

10. The method of any of clauses 1-9, wherein: the first listeningschedule comprises a first frequency-hopping sequence for a first set offrequency bands; the second listening schedule comprises a secondfrequency-hopping sequence for a second set of frequency bands; and thefirst set of frequency bands includes different frequency bands than thesecond set of frequency bands.

11. The method of any of clauses 1-10, wherein attempting to detect thenetwork discovery signal according to the first listening schedule andthe second listening schedule comprises attempting to detect the networkdiscovery signal via a hybrid listening schedule that includes the firstlistening schedule and the second listening schedule.

12. In some embodiments, a method includes: transmitting, with a firsttransceiver of a first node, a first network discovery signal using afirst physical layer mode of the first transceiver for a first timeinterval; upon expiration of the first time interval without receiving aresponse with the first transceiver to the first network discoverysignal, transmitting, with the first transceiver, a second networkdiscovery signal using a second physical layer mode of the firsttransceiver for a second time interval; and in response to the firsttransceiver receiving a response to the second network discovery signalfrom a second node, establishing, with the first transceiver, aconnection between the first node and the second node using the secondphysical layer mode.

13. The method of clause 12, wherein: transmitting the first networkdiscovery signal using the first physical layer mode comprisestransmitting the first network discovery signal with a first data rateassociated with the first physical layer mode; transmitting the secondnetwork discovery signal using the second physical layer mode comprisestransmitting the second network discovery signal with a second data rateassociated with the second physical layer mode; and the first data rateis different than the second data rate.

14. The method of clauses 12 or 13, wherein the first data rate isgreater than the second data rate.

15. The method of any of clauses 12-14, wherein transmitting the firstnetwork discovery signal using the first physical layer mode for thefirst time interval comprises: transmitting for a first time, with thefirst transceiver, the first network discovery signal using the firstphysical layer mode; and upon expiration of a first response periodwithout receiving a response to the first network discovery signal,transmitting for a second time, using the first transceiver, the firstnetwork discovery signal using the first physical layer mode.

16. The method of any of clauses 12-15, wherein transmitting the firstnetwork discovery signal for the first time comprises transmitting, withthe first transceiver, the first network discovery signal via a firstchannel associated with the first physical layer mode, and transmittingthe first network discovery signal for the second time comprisestransmitting, with the first transceiver, the first network discoverysignal via a second channel associated with the first physical layermode.

17. The method of any of clauses 12-16, further comprising, uponexpiration of a second response period without receiving a response viathe second channel to the first network discovery signal, transmitting,with the first transceiver, the first network discovery signal via athird channel associated with the first physical layer mode, wherein thesecond response period has a different duration than the first responseperiod.

18. The method of any of clauses 12-17, wherein the first responseperiod is based on a random function.

19. The method of any of clauses 12-18, wherein transmitting the secondnetwork discovery signal using the second physical layer mode for thesecond time interval comprises: transmitting for a first time, with thefirst transceiver, the second network discovery signal using the secondphysical layer mode; and upon expiration of a second response periodwithout receiving a response to the second network discovery signal,transmitting for a second time, using the first transceiver, the secondnetwork discovery signal using the second physical layer mode.

20 In some embodiments, a non-transitory computer readable medium storesinstructions that, when executed by a processor, cause the processor toperform the steps of: attempting to receive, with a first transceiverassociated with a first node, a network discovery signal from a secondnode, wherein the attempting is performed according to (a) a firstchannel-hopping sequence associated with a first physical layer mode and(b) a second channel hopping-sequence associated with a second physicallayer mode; detecting, with the first transceiver, the network discoverysignal during a slot associated with the first listening schedule; andin response to receiving the network discovery signal, establishing,with the first node, a connection between the first node and the secondnode using the first physical layer mode.

Any and all combinations of any of the claim elements recited in any ofthe claims and/or any elements described in this application, in anyfashion, fall within the contemplated scope of the present protection.

The descriptions of the various embodiments have been presented forpurposes of illustration, but are not intended to be exhaustive orlimited to the embodiments disclosed. Many modifications and variationswill be apparent to those of ordinary skill in the art without departingfrom the scope and spirit of the described embodiments.

Aspects of the present embodiments may be embodied as a system, methodor computer program product. Accordingly, aspects of the presentdisclosure may take the form of an entirely hardware embodiment, anentirely software embodiment (including firmware, resident software,micro-code, etc.) or an embodiment combining software and hardwareaspects that may all generally be referred to herein as a “module,” a“system,” or a “computer.” In addition, any hardware and/or softwaretechnique, process, function, component, engine, module, or systemdescribed in the present disclosure may be implemented as a circuit orset of circuits. Furthermore, aspects of the present disclosure may takethe form of a computer program product embodied in one or more computerreadable medium(s) having computer readable program code embodiedthereon.

Any combination of one or more computer readable medium(s) may beutilized. The computer readable medium may be a computer readable signalmedium or a computer readable storage medium. A computer readablestorage medium may be, for example, but not limited to, an electronic,magnetic, optical, electromagnetic, infrared, or semiconductor system,apparatus, or device, or any suitable combination of the foregoing. Morespecific examples (a non-exhaustive list) of the computer readablestorage medium would include the following: an electrical connectionhaving one or more wires, a portable computer diskette, a hard disk, arandom access memory (RAM), a read-only memory (ROM), an erasableprogrammable read-only memory (EPROM or Flash memory), an optical fiber,a portable compact disc read-only memory (CD-ROM), an optical storagedevice, a magnetic storage device, or any suitable combination of theforegoing. In the context of this document, a computer readable storagemedium may be any tangible medium that can contain, or store a programfor use by or in connection with an instruction execution system,apparatus, or device.

Aspects of the present disclosure are described above with reference toflowchart illustrations and/or block diagrams of methods, apparatus(systems) and computer program products according to embodiments of thedisclosure. It will be understood that each block of the flowchartillustrations and/or block diagrams, and combinations of blocks in theflowchart illustrations and/or block diagrams, can be implemented bycomputer program instructions. These computer program instructions maybe provided to a processor of a general purpose computer, specialpurpose computer, or other programmable data processing apparatus toproduce a machine. The instructions, when executed via the processor ofthe computer or other programmable data processing apparatus, enable theimplementation of the functions/acts specified in the flowchart and/orblock diagram block or blocks. Such processors may be, withoutlimitation, general purpose processors, special-purpose processors,application-specific processors, or field-programmable gate arrays.

The flowchart and block diagrams in the figures illustrate thearchitecture, functionality, and operation of possible implementationsof systems, methods and computer program products according to variousembodiments of the present disclosure. In this regard, each block in theflowchart or block diagrams may represent a module, segment, or portionof code, which comprises one or more executable instructions forimplementing the specified logical function(s). It should also be notedthat, in some alternative implementations, the functions noted in theblock may occur out of the order noted in the figures. For example, twoblocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved. It will also be notedthat each block of the block diagrams and/or flowchart illustration, andcombinations of blocks in the block diagrams and/or flowchartillustration, can be implemented by special purpose hardware-basedsystems that perform the specified functions or acts, or combinations ofspecial purpose hardware and computer instructions.

While the preceding is directed to embodiments of the presentdisclosure, other and further embodiments of the disclosure may bedevised without departing from the basic scope thereof, and the scopethereof is determined by the claims that follow.

What is claimed is:
 1. A method comprising: attempting to detect, with afirst transceiver associated with a first node, a network discoverysignal from a second node, wherein the attempting is performed accordingto (a) a first listening schedule associated with a first physical layermode and (b) a second listening schedule associated with a secondphysical layer mode; detecting, with the first transceiver, the networkdiscovery signal during a slot associated with the first listeningschedule; and in response to detecting the network discovery signal,establishing, with the first node, a connection between the first nodeand the second node using the first physical layer mode.
 2. The methodof claim 1, wherein the network discovery signal comprises at least aheader portion of a network discovery frame.
 3. The method of claim 1,wherein the network discovery signal is received from the second nodeattempting to join a network that includes the first node.
 4. The methodof claim 1, wherein the first physical layer mode comprises a first datarate and the second physical layer mode comprises a second data ratethat is different than the first data rate.
 5. The method of claim 1,wherein the first physical layer mode comprises a first data rate andthe second physical layer mode comprises a second data rate that islower than the first data rate.
 6. The method of claim 5, wherein thesecond listening schedule includes a slot that has an active period inwhich the network discovery signal can be detected and an inactiveperiod in which the network discovery signal cannot be detected.
 7. Themethod of claim 6, wherein each slot included in the second listeningschedule has a respective active period in which the network discoverysignal can be detected and a respective inactive period in which thenetwork discovery signal cannot be detected.
 8. The method of claim 6,wherein the inactive period temporally overlaps one or more slotsassociated with the first listening schedule.
 9. The method of claim 6,wherein the active period has a longer duration than the slot associatedwith the first listening schedule.
 10. The method of claim 1, wherein:the first listening schedule comprises a first frequency-hoppingsequence for a first set of frequency bands; the second listeningschedule comprises a second frequency-hopping sequence for a second setof frequency bands; and the first set of frequency bands includesdifferent frequency bands than the second set of frequency bands. 11.The method of claim 1, wherein attempting to detect the networkdiscovery signal according to the first listening schedule and thesecond listening schedule comprises attempting to detect the networkdiscovery signal via a hybrid listening schedule that includes the firstlistening schedule and the second listening schedule.
 12. A methodcomprising: transmitting, with a first transceiver of a first node, afirst network discovery signal using a first physical layer mode of thefirst transceiver for a first time interval; upon expiration of thefirst time interval without receiving a response with the firsttransceiver to the first network discovery signal, transmitting, withthe first transceiver, a second network discovery signal using a secondphysical layer mode of the first transceiver for a second time interval;and in response to the first transceiver receiving a response to thesecond network discovery signal from a second node, establishing, withthe first transceiver, a connection between the first node and thesecond node using the second physical layer mode.
 13. The method ofclaim 12, wherein: transmitting the first network discovery signal usingthe first physical layer mode comprises transmitting the first networkdiscovery signal with a first data rate associated with the firstphysical layer mode; transmitting the second network discovery signalusing the second physical layer mode comprises transmitting the secondnetwork discovery signal with a second data rate associated with thesecond physical layer mode; and the first data rate is different thanthe second data rate.
 14. The method of claim 13, wherein the first datarate is greater than the second data rate.
 15. The method of claim 12,wherein transmitting the first network discovery signal using the firstphysical layer mode for the first time interval comprises: transmittingfor a first time, with the first transceiver, the first networkdiscovery signal using the first physical layer mode; and uponexpiration of a first response period without receiving a response tothe first network discovery signal, transmitting for a second time,using the first transceiver, the first network discovery signal usingthe first physical layer mode.
 16. The method of claim 15, whereintransmitting the first network discovery signal for the first timecomprises transmitting, with the first transceiver, the first networkdiscovery signal via a first channel associated with the first physicallayer mode, and transmitting the first network discovery signal for thesecond time comprises transmitting, with the first transceiver, thefirst network discovery signal via a second channel associated with thefirst physical layer mode.
 17. The method of claim 16, furthercomprising, upon expiration of a second response period withoutreceiving a response via the second channel to the first networkdiscovery signal, transmitting, with the first transceiver, the firstnetwork discovery signal via a third channel associated with the firstphysical layer mode, wherein the second response period has a differentduration than the first response period.
 18. The method of claim 15,wherein the first response period is based on a random function.
 19. Themethod of claim 12, wherein transmitting the second network discoverysignal using the second physical layer mode for the second time intervalcomprises: transmitting for a first time, with the first transceiver,the second network discovery signal using the second physical layermode; and upon expiration of a second response period without receivinga response to the second network discovery signal, transmitting for asecond time, using the first transceiver, the second network discoverysignal using the second physical layer mode.
 20. A non-transitorycomputer readable medium storing instructions that, when executed by aprocessor, cause the processor to perform operations comprising:attempting to receive, with a first transceiver associated with a firstnode, a network discovery signal from a second node, wherein theattempting is performed according to (a) a first channel-hoppingsequence associated with a first physical layer mode and (b) a secondchannel hopping-sequence associated with a second physical layer mode;detecting, with the first transceiver, the network discovery signalduring a slot associated with the first listening schedule; and inresponse to receiving the network discovery signal, establishing, withthe first node, a connection between the first node and the second nodeusing the first physical layer mode.